CBG-Based HARQ-ACK Feedback for 5G Retransmission
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Solution Overview
Problem
Current LTE systems face inefficiencies in retransmission mechanisms for code block group-based HARQ operations, particularly due to the use of one-bit HARQ-ACK feedback for transport blocks, which can lead to substantial resource consumption when retransmitting large numbers of code blocks.
Innovation Solution
Implementing HARQ-ACK feedback mechanisms based on code blocks or groups of code blocks (CBGs) to efficiently retransmit and receive unsuccessfully decoded data, utilizing a single physical downlink control channel to schedule both new transport blocks and retransmissions of CBGs, and employing mini-slot structures for more granular control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If one-bit HARQ-ACK feedback is used for transport blocks, then the feedback mechanism is simple, but resource consumption increases substantially when retransmitting large numbers of code blocks
Solution Approach 1:
The patent segments the transport block into multiple code block groups (CBGs) and provides individual HARQ-ACK feedback for each CBG. This segmentation allows the system to identify and retransmit only the failed CBGs rather than retransmitting the entire transport block, thereby reducing resource consumption while maintaining manageable feedback complexity through structured grouping.
2Productivity
If code block group-based HARQ operations are implemented, then retransmission efficiency improves, but signaling overhead increases
Solution Approach 1:
The patent merges multiple CBG feedback bits into a compact HARQ-ACK codebook structure that can be transmitted efficiently. By combining the feedback for multiple CBGs into a unified signaling mechanism and utilizing the physical uplink control channel (PUCCH) or physical uplink shared channel (PUSCH) for consolidated transmission, the system reduces signaling overhead while maintaining the efficiency benefits of CBG-based operations.
3Quantity of substance
If a single physical downlink control channel schedules both new transport blocks and retransmissions, then resource allocation is optimized, but scheduling complexity increases
Solution Approach 1:
The patent implements dynamic scheduling where the single physical downlink control channel (PDCCH) can flexibly indicate different types of transmissions (new transport blocks or CBG retransmissions) based on current channel conditions and buffer status. The dynamic nature of the scheduling allows optimized resource allocation by adapting to real-time network conditions, while the use of standardized DCI formats and CBG indication mechanisms keeps the scheduling complexity manageable.
Data Source
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AI summary
In 5G systems, to provide higher data rates, a large number of code blocks (CBs) for one transport block may be transmitted in a single slot. Given that a large number of code blocks would be supported in 5G, one-bit hybrid automatic repeat request acknowledgements or non-acknowledgements (HARQ-ACKs) for one transport block may not be desirable. Described herein are mechanisms for utilizing HARQ-ACKs based upon code blocks (CBs) or groups of CBs, referred to as code block groups (CBGs), to more efficiently retransmit and receive unsuccessfully decoded data.